Exercise devices, and in particular weight training machines, typically include a mechanical member that the user repeatedly moves along a prescribed path for exercise. Conventionally, movement of the mechanical member is resisted in some fashion (often by weights) to render the movement more difficult and thereby intensify the exercise. The movement of the mechanical member determines what muscle or muscle groups are to be involved in the exercise.
One popular exercise movement is the leg press, which involves straightening the legs from a position in which they are bent at approximately a ninety degree angle at the knees and in which the exerciser's knees are drawn somewhat near the chest. Generally, the leg press movement exercises the quadriceps, gluteals, and hamstrings of the exerciser.
The leg press movement can be carried with different types of apparatus. For example, some machines are configured such that the exerciser lays on his back with the thighs generally upright and applies a generally horizontal force against a foot panel with the heels. Such machines have a platform supporting the exerciser that slides rearwardly as he pushes his feet against a foot panel, or a configuration in which the foot panel moves relative to the frame in response to the exerciser pushing against it. Such a machine is exemplified by the NITRO™ Leg Press, available from Nautilus HPS, Inc., Independence, Va. As another example, machines exist in which the exerciser is in a generally upright or inclined seated position with his back placed against a backrest and applies a generally horizontal force through the heels against a foot panel. These machines can also have a design in which the seat and backrest slide relative to the frame, or a stationary seat design, in which the foot panel moves relative to the frame. An exemplary machine of this type having a stationary seat is the 2ST leg press machine, available from Nautilus HPS, Inc., Independence, Va. (also illustrated in U.S. Pat. No. 5,106,081).
Another leg press machine is the inclined leg press, which includes a stationary seat and an adjustably weighted sled that slides on inclined rails (typically the rails are disposed at an angle of between about 35 and 45 degrees to the underlying surface). Inclined leg press machines are preferred by some exercisers for several reasons: they can induce significant hip flexion and rotation during exercise; the weight resistance is typically relatively constant over the exercise stroke (which is often not the case for other machines, particularly those that rely on linkages and/or cams to transfer resistance to the exerciser); and the amount of resistance can be precisely applied (the resistance can vary for sled-type designs in which the exerciser's body moves during the exercise stroke).
One issue that can arise with leg press machines is the angle at which force is applied to the foot panel. Ideally, this force should be applied parallel to the tibia of the user (i.e., the foot panel is normal to the user's tibia) to reduce shear stress on the knee joint and to increase exercise efficiency. With a sled-type design in which the body of the exerciser moves during the exercise stroke, typically the foot panel is stationary, so the angle of the tibia to the foot panel varies as the leg straightens. With a typical simple swing arm-type design in which the foot pad moves relative to the frame, the foot panel tends to increase its angle relative to the exerciser's back as the foot panel moves away from the user. Unfortunately, this variation in angle should decrease in order to maintain the desired ninety degree angle with the tibia. One approach to address this problem is illustrated in the Nautilus 2ST leg press machine discussed above, in which a pair of swing arms interconnect with a base and a member connected to the foot pad to decrease the angle of the foot pad in the desired manner. However, this issue has not been addressed with an inclined leg press.